Chip formation and surface integrity investigation considering the minimum uncut chip thickness in micro-helical milling

In micro-helical milling, the minimum uncut chip thickness (MUCT) plays a crucial role in governing chip formation and surface integrity. However, its precise determination and underlying influence mechanisms in micro-helical milling remain insufficiently explored. Additionally, the residual stress on micro-hole walls is a key factor affecting the performance and longevity of machined components, yet investigations into residual stress characteristics in micro-helical hole milling are still limited. To address these gaps, this study investigates the chip formation mechanisms and surface integrity in micro-helical milling, with a focus on the unique effects of MUCT. Finite element simulations were conducted to determine the MUCT values for 3J33 maraging steel in micro-helical milling, ranging from 30 % to 36.7 % of the cutting-edge radius. Based on these simulations, a series of micro-helical milling experiments were performed to examine the interrelations between cutting parameters (incorporating MUCT considerations) and variations in surface roughness and residual stress. The results were optimized using response surface methodology, identifying optimal cutting conditions (cutting velocity of 44 m/min, tangential feed per tooth of 6.4 μm, and axial pitch of 0.3 mm). This study provides new insights into the influence of MUCT on surface integrity and material removal mechanisms, advancing the understanding of micro-helical milling and facilitating its broader industrial application.